WHICH OF THE FOLLOWING HEMOGLOBINOPATHIES DOES NOT CAUSE SICKLE-CELL CRISIS

• A. Hemoglobin SA ✓
• B. Hemoglobin SS
• C. Hemoglobin SC
• D. Hemoglobin S/β-thalassemia

 

Hemoglobinopathies are a group of genetic disorders characterized by abnormalities in the structure or production of hemoglobin, the protein responsible for carrying oxygen in red blood cells. Sickle-cell disease is one of the most well-known hemoglobinopathies, caused by a mutation in the HBB gene that leads to the production of abnormal hemoglobin known as hemoglobin S (HbS). This abnormal hemoglobin can polymerize under certain conditions, causing red blood cells to become rigid and take on a characteristic sickle shape. The sickle-shaped cells can block blood flow, leading to vaso-occlusive crises and tissue damage.

Different Types of Hemoglobinopathies

1. Hemoglobin SA: Hemoglobin SA is a heterozygous condition where an individual inherits one normal adult hemoglobin gene (HbA) and one sickle cell gene (HbS). Individuals with this genotype are carriers of sickle-cell trait but typically do not experience symptoms of sickle-cell disease. They are generally asymptomatic carriers who do not develop sickle-cell crisis.
2. Hemoglobin SS: Hemoglobin SS results from inheriting two copies of the HbS gene, one from each parent. This genotype causes sickle-cell disease, where individuals are prone to recurrent vaso-occlusive crises known as sickle-cell crises. These crises can manifest with severe pain, organ damage, and other complications due to the blockage of blood vessels by sickled red blood cells.
3. Hemoglobin SC: Hemoglobin SC is a compound heterozygous condition where an individual inherits one HbS gene and one HbC gene. While individuals with this genotype can experience some clinical manifestations similar to those with hemoglobin SS, they typically have milder symptoms and fewer complications compared to hemoglobin SS.
4. Hemoglobin S/β-thalassemia: Hemoglobin S/β-thalassemia is a condition where individuals inherit one HbS gene along with mutations in the beta-globin gene that cause reduced production of normal adult hemoglobin (HbA). The clinical presentation can vary depending on the specific mutations involved but often results in symptoms similar to those seen in individuals with sickle-cell disease.

Identifying the Hemoglobinopathy that Does Not Cause Sickle-Cell Crisis

Based on the information provided above:

The correct answer is:

A. Hemoglobin SA

Individuals with Hemoglobin SA do not typically experience sickle-cell crisis as they are carriers of the sickle cell trait without developing full-blown sickle-cell disease.

In summary, while Hemoglobins SS, SC, and S/β-thalassemia can all lead to sickle-cell crisis due to the presence of abnormal hemoglobin S, Hemoglobin SA does not cause such crises as it represents a carrier state without significant clinical symptoms.

In other words, Hemoglobinopathies are a group of genetic disorders characterized by abnormalities in the structure or production of hemoglobin, the protein in red blood cells that carries oxygen throughout the body. Sickle-cell crisis is a complication associated with sickle cell disease, a type of hemoglobinopathy where the hemoglobin S mutation leads to the formation of abnormal, sickle-shaped red blood cells. During a sickle-cell crisis, these abnormal cells can block blood flow, leading to pain and other serious complications.

Among the options provided:

A. Hemoglobin SA: Hemoglobin SA is a normal variant of hemoglobin found in individuals who have inherited one normal adult hemoglobin gene (A) and one sickle cell gene (S). Individuals with this genotype are carriers of sickle cell trait but do not typically experience sickle-cell crisis unless under extreme conditions such as high altitude or low oxygen levels.

B. Hemoglobin SS: Hemoglobin SS refers to individuals who have inherited two copies of the sickle cell gene (S), resulting in sickle cell anemia. These individuals are prone to frequent sickle-cell crises due to the presence of predominantly abnormal hemoglobin S.

C. Hemoglobin SC: Hemoglobin SC results from inheriting one copy each of the HbS and HbC genes. Individuals with this genotype may experience some symptoms similar to those with sickle cell anemia, but they generally have a milder clinical course compared to HbSS individuals and may have fewer sickle-cell crises.

D. Hemoglobin S/β-thalassemia: Hemoglobin S/β-thalassemia is a condition where one abnormal hemoglobin S gene is inherited along with one β-thalassemia gene. This condition can result in varying degrees of anemia and symptoms similar to those seen in sickle cell disease, including the potential for sickle-cell crises.

Among these options, Hemoglobin SA (sickle cell trait) does not typically cause sickle-cell crisis under normal circumstances. However, it is important to note that individuals with sickle cell trait can still experience complications under certain conditions such as extreme physical exertion or dehydration.